Detector and localizer for low energy radiation emissions

ABSTRACT

A detector particularly suited for use in immuno-guided surgery capable of detecting very faint gamma emissions and thereby localizing cancerous tumor. The detector employs a hand manipular probe within which is contained a crystal such as cadmium telluride which is secured in a light-tight environment. A noise immune structuring of the probe and crystal combination includes the utilization of electrically conductive, compliant cushion layer located at one face of the crystal in conjunction with freely abutting biasing and ground contacts. A nylon, resilient retainer is positioned in tension over the assemblage of crystal, ground and biasing contacts and compliant layers to achieve a compressively retained assemblage. A dead air space is developed between the forward facing window of the probe and the crystal retaining assemblage.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.07/271,023, filed Nov. 14, 1988, "Detector and Localizer for Low EnergyRadiation Emissions, by Denen, et al., now abandoned, and is acontinuation-in-part of application Ser. No. 248,920, filed Sept. 23,1988, now U.S. Pat. No. 4,893,013, which is a continuation-in-part ofapplication Ser. No. 027,197, field Mar. 17, 1987, now U.S. Pat. No.4,801,803, all of the aforesaid applications and patents being assignedin common herewith.

BACKGROUND

The detection and treatment of cancerous tissue has been the subject ofintense investigation for many years. One among the many approaches toits detection has concerned the identification of tumor specificantigens. Where these antigens can be identified, radionucleid labeledantibodies have been employed which tend to collect at tumor sites. Whenso concentrated, somewhat elaborate radiation detection equipment thenis employed to record, for example, by imaging the concentrations of theemissive substances and thus to locate neoplastic tissue. Importantadvances in this procedure have been evidenced through the use ofmonoclonal antibodies or fragments thereof with a variety ofradionucleides. Typical techniques for carrying out imaging of theseantibodies have involved, for example, tomographic scanning,immunoscinitigraphy and the like. The particular choice of radionucleidfor labeling antibodies is dependent upon its nuclear properties, thephysical half life, the detection instrument capabilities, thepharmacokinetics of the radiolabeled antibody, and the degree ofdifficulty of the labeling procedure. The most widely used of theseradionucleides in nuclear medicine imaging include technetium, ^(99m)Tc, iodine ¹²⁵ I, ¹³¹ I, and indium, ¹¹¹ In. Of the above, forlocalizing tumors of the gastro-intestinal tract, the radionucleid ¹³¹ Iis used as the marker or label in conjunction with imaging gamma camerasand the like which are relative large and elabroate devices positionedabove the patient during the imaging process.

In spite of its somewhat extensive utilization, ¹³¹ I is not an idealradionucleid for use in diagnositc medicine. The high energygamma-photon emitted from ¹³¹ I is poorly detected by the classic gammacamera and like instrumentation. In addition, the administered markeremissions deliver a high radiation dose to the patient. Further, theimaging definition of these external imaging devices has not beensatisfactory for many reasons. As tumor sites become smaller, theradionucleid concentration thereat will tend to be lost, from an imagingstandpoint, in the background or blood pool radiation necessarilypresent in the patient.

Over the recent past, a surgical procedure has been developed concerningthe differentiation and removal of such neoplastic tissue through theuse of much lower energy gamma emission levels for example, ¹²⁵ I(27-35kev). While such a radiolabel cannot be employed with conventionalexternal imaging or scanning devices because the radiation is stronglyabsorbed by the tissue intermediate between the tumor and the surface ofthe patient's body, it has been found that when employed with a probetype detection structure, a highly effective differentiation techniquecan be evolved. More particularly, the longer half like of this type ofradiolabel coupled with a surgical methodology involving the waiting ofappropriate intervals from the time of introduction of the radiolabelledantibody to the patient to the time of surgery, can evolve a highlyaccurate differentiation of cancerous tumor. This improved method oflocalization, differentiation and removal of cancerous tumor involves asurgical procedure wherein the patient suspected of containingneoplastic tissue is administered an effective amount of an antibodyspecific for neoplastic tissue which is labeled with a radioactiveisotope as above-noted exhibiting photon emissions of specific energylevels. Next, the surgical procedure is delayed for a time intervalfollowing such administration for permitting the labeled antibody topreferentially concentrate in any neoplastic tissue present in thepatient, as well as to be cleared from normal tissue so as to increasethe ratio of photon emissions from the neoplastic tissue to thebackground photon emissions. Thereafter, an operative field of thepatient is surgically accessed and tissue within the operative field tobe examined for neoplastic tissue has the background photon emissioncount determined. Once the background photon emission count for thetissue within the operative field has been determined, this hand-heldprobe is manually positioned within the operative field adjacent tissuesuspected of being neoplastic. Readouts then can be achieved from probecounting for differentiation. In the above regard, reference is made tothe following technical publications:

I. "CEA-Directed Second-Look Surgery in the Asymptomatic Patient afterPrimary Resection of Colorectal Carcinoma", E. W. Martin, Jr., MD, J. P.Minton, MD, PhD, Larry C. Carey, MD. Annals of Surgery 202:1 (Sept. 1985301-12.

II. "Intraoperative Probe-Directed Immunodetection Using a MonoclonalAntibody", P. J. O'Dwyer, MD, C. M. Mojzsik, RN MS G. H. Hinkle, RPh,MS, M. Rousseau, J. Olsen, MD, S. E. Tuttle, MD, R. F. Barth, PhD, M.O.Thurston, PhD D. P. McCabe, MD, W. B. Farrar, MD, E. W. Martin, Jr., MD.Archives of Surgery 121 (Dec. 1986) 1321-1394.

III. "Intraoperative Radioimmunodetection of Colorectal Tumors with aHand-Held Radiation Detector", D. T. Martin, MD, G. H. Hinkle, MS RPh,S. Tuttle MD, J. Olsen, MD, H. Abdel-Nabi, MD, D. Houschens, PhD, M.Thurston, PhD, E. W. Martin, Jr., MD, American Journal of Surgery, 150:6(Dec. 1985) 672-75.

IV. "Portable Gamma Probe for Radioimmune Localization of ExperimentalColon Tumor Xenografts", D. R. Aitken, MD, M. O. Thurston, PhD, G. H.Hinkle, MS RPh, D. T. Martin, MD, D. E. Haagensen, Jr., MD, PhD, D.Houchens, PhD, S. E. Tuttle, MD E. W. Martin, Jr., MD. Journal ofSurgical Research, 36:5 (1984) 480-489.

V. "Radioimmunoguided Surgery: Intraoperative Use of Monoclonal Antibody17-1A in Colorectal Cancer". E. W. Martin, Jr., MD, S. E. Tuttle, MD, M.Rousseau, C. M. Mojzisik, RN MS, P. J. O'Dwyer, MD, G. H. Hinkle, MSRPh, E. A. Miller, R. A. Goodwin, O. A. Oredipe, MA, R. F. Barth, MD, J.O. Olsen, MD, D. Houchens, PhD, S. D. Jewell, MS, D. M. Bucci, BS, D.Adams, Z. Steplewski, M. O. Thurston, PhD, Hybridoma, 5 Suppl 1 (1986)S97-108.

Reference further is made to commonly assigned U.S. Pat. No. 4,782,840,entitled "Method for Locating, Differentiating, and Removing Neoplasms"by Edward W. Martin Jr., and Marlin O. Thurston, issued Nov. 8, 1988.

The success of this highly effective differentiation and localizationtechnique is predicated upon the availability of a probe-type detectingdevice capable of detecting extremely low amounts of radiationnecessarily developed with the procedure. In this regard, low energyradionucleides are used such as ¹²⁵ I and the distribution ofradiolabeled antibody with the nucleid is quite sparse so thatbackground emissions can be minimized and the ratio of tumor-specificcounts received to background counts can be maximized. Conventionalradiation detection probe-type devices are ineffective for this purpose.Generally, because a detection device is required for the probes whichis capable of performing at room temperatures, a very fragile ordelicate detection crystal such as cadmium telluride is employed. Theprobe using such a crystal must be capable of detecting as little as asingle gamma ray emission which may, for example, create electron-holepairs in the crystal of between about 2,000 and 4,000 electrons.Considering that an ampere generates 6.25×10¹⁸ electrons per second, onemay observe that extremely small currents must be detectable with such aprobe. However, the probe system also must be capable of discriminatingsuch currents from any of a wide variety of electrical disturbances, forexample which may be occasioned from cosmic inputs, room temperaturemolecular generated noise, and capacitively or piezoelectrically inducednoise developed from the mere manipulation of the probe itself. Whilebeing capable of performing under these extreme criteria, the same probefurther must be capable of performing under the requirements of thesurgical theater. In this regard, it must be secure from ingress ofcontaminants; it must be sterilizable; and it must be rugged enough towithstand manipulation by the surgeon within the operating roomenvironment. Further, the system with which the probe is employed, mustbe capable of perceptively apprising the surgeon of when neoplastictissue is being approached such that the device may be employed for thepurpose of guiding the surgeon to the situs of cancer. Additionally, forsurgical use, the probe instrument must be small, so as to beeffectively manipulated through surgical openings and the like. Suchdimunitive size is not easily achieved under the above operationalcriteria. This technique has been described as "radioimmuno-guidedsurgery", a surgical approach developed by E. W. Martin, Jr., MD, and M.O. Thurston, PhD.

In addition to the capability of performing under the above-notedrelatively extreme criteria, the probe instrument called upon for theinstant use preferably should be fabricable employing practicalmanufacturing techniques. One approach to improving the fabricability ofthe probe instruments is described in application for U.S. patent Ser.No. 07/248,920 by Denen, et al., entitled "Detector and Localizer forLow Energy Radiation Emissions", filed Sept. 23, 1988, now U.S. Pat. No.4,893,013, issued Jan. 9, 1990. The probe structuring disclosed thereinis one wherein necessary ground and bias are applied to opposite sidesof the gamma detecting crystal utilizing electrodes which are fixed tothe crystal face. An elastomeric retainer is used to structurally retainall the components together including the crystal, the biasingarrangement, and the like. While successful production has been achievedwith the structure so described, the technique described therein is onerequiring the use of a multi-component cap for the assembly and onewherein deterioration has been noted in the coupling of the bias andgrounding electrodes to the radiation responsive crystals. Furtherimprovements in the structure of the probe have been deemed necessaryboth in terms of the integrity of the association of external componentswith the gamma radiation crystal as well as in conjunction with the easeof fabricability of the probe.

SUMMARY

The present invention is addressed to apparatus for detecting andlocating sources of emitted radiation and, particularly, sources ofgamma radiation as well as the method of fabricating such apparatus.Detection is achieved under room temperature conditions using a crystalsuch as cadmium telluride and with respect to very low energy emissions.To achieve the extreme sensitivity capabilities of the apparatus, aninstrumentation approach has been developed in which the somewhatfragile crystal is securely retained in isolation from externallyinduced incidents otherwise creating excessive noise. In this regard,microphonic effects are minimized through employment of a sequence ofmaterials exhibiting divergent acoustic impedances. Capacitive orpiezoelectric effects occasioned by the most minute of intercomponentmovements are controlled to acceptable levels. Compressive retention ofthe crystal and electrical contacts with it is employed in conjunctionwith electrically conductive but pliable surface supports. Theinstrument also achieves performance while being structured for assemblyby practical manufacturing techniques.

A feature of the invention provides an instrument for detecting andlocating sources of radiation emissions having predetermined energylevels which includes a housing having a forwardly disposed portion. Acrystal mount is presented which is positioned within the housingforwardly disposed portion and which is formed of materials attenuatingradiation of the predetermined energy levels and which has a forwardlydisposed, crystal receiving cavity extending inwardly thereinto from aforwardly disposed receiving cavity extending inwardly thereinto from aforwardly disposed opening. A resilient electrically insulativepolymeric layer is positioned within the cavity and a radiationresponsive crystal is located within the cavity which has a rearwardlydisposed surface positioned facing the electrically insulative layer andhas a side portion extending to a forwardly disposed surface. A biasingarrangement extends within the cavity to provide a bias contact adjacentthe electrically insulative layer and a first electrically conductivecompliant member which is conformable with and in contacting adjacencybetween the crystal rearwardly disposed surface and the bias contact isprovided. A second electrically conductive compliant member which isconformable with and in contacting adjacency with the crystal forwardlydisposed surface is provided and a grounding arrangement is positionedin abutting adjacency with the second compliant member for electricallygrounding the crystal forwardly disposed surface. A resilient retaineris positioned in tension over the grounding arrangement and the crystalforwardly disposed surface for compressively retaining componentsincluding the ground and the second compliant member against the crystalforwardly disposed surface and the rearwardly disposed surface of thecrystal against the first compliant member, the bias contract and thepolymeric layer to an extent effective to provide a stabilization of theelectrical contacts to the crystal derived from the biasing arrangementand the grounding arrangement and to retain the components in astatically stable state. A forward cover is positioned to enclose thecrystal mount, crystal receiving cavity, the crystal, the groundingarrangement, and the resilient retainers for permitting transmission ofthe radiation emission of predetermined energy levels.

Another feature of the invention provides an instrument for detectingsources of radiation emissions which includes a housing having aforwardly disposed portion. A crystal mount is positioned within thehousing forwardly disposed portion having an electrically insulativeforwardly disposed crystal supporting surface. A radiation responsivecrystal having a rearwardly disposed surface is positioned facing thecrystal mount crystal supporting surface and has a side portionextending to a forwardly disposed surface. Further, an electrical biasarrangement having a bias contact at the crystal mount crystalsupporting surface is provided as well as a first electricallyconductive compliant cushioning member conformable with and incontacting adjacency between the crystal rearwardly disposed surface andthe bias contact. A second electrically conductive compliant cushioningmember is conformable with and in contacting adjacency with the crystalforwardly disposed surface and a grounding arrangement is positioned inadjacency with the second compliant member for electrically groundingthe crystal forwardly disposed surface. A resilient retainer arrangementis positioned in tension over the second electrically conductivecompliant cushion member for compressively retaining the secondelectrically conductive compliant cushioning member upon the crystalmount supporting surface and a forward cover is positioned over and inenclosing relationship with the crystal mount, the crystal supportingsurface, the crystal and the first and second electrically compliantcushioning members for excluding external contaminants, and having aforwardly disposed window portion surface, formed of material permittingsubstantial transmission of the radiation emission to the crystalforwardly disposed surface, the window portion being spaced forwardlyfrom the crystal to define a dead air space for enhancing the acousticisolation of the crystal.

As another feature, the invention provides an instrument for detectingsources of gamma radiation emissions which includes a housing having aforwardly disposed portion. A crystal mount is positioned within thehousing forwardly disposed portion having an electrically insulativeforwardly disposed crystal supporting surface. A gamma radiationresponsive crystal having a rearwardly disposed surface is positionedfacing the crystal mount crystal supporting surface and has a sidesurface extending to a forwardly disposed surface. A compliantcushioning arrangement for locating the crystal upon the crystalsupporting surface with substantial immunity from externally inducedvibration phenomena is provided and electrical biasing is provided forapplying an electrical bias to the crystal rearwardly disposed surface.Similarly, a grounding arrangement is provided for electricallygrounding the crystal forwardly disposed surface. A resilient retainerarrangement is positioned in tension over the gamma radiation responsivecrystal, the compliant cushioning arrangement, the electrical biasingarrangement, and the grounding arrangement for effecting the retentionthereof in compression upon the crystal mount crystal supportingsurface. Finally, a forward cover is positioned over and in enclosingrelationship with the crystal mount crystal supporting surface, thecrystal, the compliant cushioning arrangement, and the groundingarrangement for excluding external contaminants and is seen to have aforwardly disposed window portion formed of material permittingsubstantial transmission of gamma radiation to the crystal forwardlydisposed surface. The window portion is spaced forwardly from thecrystal to define a space enhancing the isolation of the crystal fromexternally induced vibration phenomena.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

The invention accordingly, comprises the apparatus possessing theconstruction, combination of elements, and arrangement of parts whichare exemplified in the following detailed disclosure. For a fullerunderstanding of the nature and objects of the invention, referenceshould be had to the following detailed description taken in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the probe instrument and associatedconsole representing the instrumentation of the invention;

FIG. 2 is a side elevational view of the probe instrument shown in FIG.1 with portions broken away to reveal internal structure;

FIG. 3 is an exploded view of the forward assemblage of the instrumentof FIG. 2;

FIG. 4 is a sectional view of the forward portion of the instrumentembodiment represented in FIG. 3;

FIG. 5 is a partial sectional view showing a tooling arrangement forproviding an electrically insulated layer within the cavity of a crystalretainer of the instrument of FIGS. 2 and 3;

FIG. 6 is a perspective view showing the component assemblage of theinstrument of FIGS. 2 and 3 which is developed during the fabricationthereof;

FIG. 7 is another perspective view of the instrument of FIGS. 2 and 3showing a next step in the assembly procedure thereof;

FIG. 8 is a side view of the probe instrument of FIG. 2 showing itsemployment with a sterile cover or sheath; and

FIGS. 9A and 9B combine as labeled to form a block diagram of thefunctional components of the control system associated with theinstrument of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an embodiment of the probe and supportinginstrumentation of the invention particularly designed for employment inthe medical-surgical field is represented generally at 10. Thisassemblage includes a hand-manipular probe represented generally at 12which is coupled by a triaxial cable 14 to a console 16. The probe 12,which preferably is retained by the surgeon within a disposablepolymeric sheath or cover is maneuvered about the region of surgicalinterest to locate tumerous tissue for resection. When used inconjunction with colonic surgery, for example, the probe 12 ismaneuvered through a surgical opening in the body cavity and essentiallybrought into contact with organs under study by the surgeon. Whenemployed in a radioimmuno-guided mode, a loudspeaker or annunciatorwithin the console 16 may be activated to provide a "siren" form ofoutput which apprises the surgeon that the probe 12 is at a site ofcancer. Thus, it is necessary that the device 12 be of convenient lengthand comfortable to grasp. The probe 12 is seen to include a radiationacceptance surface or window 18 located at the tip of an angularlyoriented portion thereof 20. Portion 20 extends from a hand-grippableportion 22 at an angle of about 30° to facilitate its maneuverabilityabout the back or hidden side of organs and, preferably, is coated witha low-friction surface material such as TEFLON (polytetrafluoroethylene)to enhance noise avoidance otherwise occasioned by the rubbing ofsurface 18 over tissue and the like during surgery.

Because the assemblage 10 is used in a surgical theater, the console 16also is readily cleaned, having a smooth, one-piece touch sensitivepolymeric surface 24 surmounting a relatively large LCD readout ordisplay 26, a dual colored LED readout 28 and a sequence offinger-actuated switches. These switches or keyboard, as representedgenerally at 30 permit the microprocessor driven console 16 to carry outan instructive or "user friendly" dialogue with the practitioner. Forpurpose of safety, the device is powered by a rechargeable battery.

In addition to conventional on and off switches shown, respectively, at32 and 33, the switches provided on the console 16 include a count modeswitch 34, a sound switch 35, a reset count switch 36, a squelchfunction switch 37, a calibration function switch 38, and up and downincrementing switches for adjustment within certain of the switchgenerated modes as shown, respectively, at 30 and 40.

The probe 12 must be capable of performing essentially at roomtemperature. Thus, the device employs a cadmium telluride crystal and,because of the preferred low energy levels of radiation which it iscalled upon to detect, must be capable of operatively reacting to lowenergy gamma ray interactions. The interaction of gamma rays with suchcrystals is primarily through three processes, namely the photo-electriceffect, Compton scattering, and pair production. In the photo-electriceffect, a photon of energy, hv, interacts with an atom as a whole. Itsenergy is completely transferred to an electron, usually in theinnermost shell. The electron is ejected with a kinetic energy: e_(kin)=hv-E_(b), where E_(b) is the binding energy of the orbital electron, his Planck's constant, and v is the frequency associated with the wavenature of the gamma radiation. Such electrons undergo many collisionsuntil this energy is shared with some thousands of other electrons. Eachof these electrons leaves behind a positively charged region called inthe literature a "hole". At the energies of ¹²⁵ I Compton scattering isof minor importance. Pair production refers to the reaction of anelectron and a photon to the gamma ray. Since this process requires morethan 1.0 Mev it does not occur in the present application. In Comptonscattering, the primary photon may interact with any one of the orbitalelectrons. The electrons are considered essentially as free electronsunder the condition that the primary photon energy is large comparedwith the electron binding energy. The interaction may be analyzed as theelastic collision between the primary photon and the electron. Energy isshared between the recoil electron and the secondary photon. Thissecondary photon travels in a direction different from that of theprimary photon, and is referred to as the scattered photon.

Thus, as an incoming gamma ray is absorbed by the crystal, it transferssome or all of its energy to electrons, which as charged particles passthrough the semiconductor producing electron-hole pairs and, therefore,the capability of charge-transfer within the crystal medium.

when a charge particle produces electron-hole pairs in thesemiconductor, the electric field causes these charge carriers to movetoward and accumulate at the appropriate electrodes. As these chargesmove toward or are collected at the electrodes, they induce a charger orelectrical pulse signal in the circuit external to the detector. It isthen necessary to pre-amplify these signals and feed them to theelectronics of the control unit or console 16.

For effective performance, the probe 12 must be capable of generatingand discerning signals representing gamma ray strikes which are ofextremely low energy. In this regard, a gamma ray interaction with thecadmium telluride crystal may produce two to four thousand electrons. Itbeing recognized that 6.25×10¹⁸ electrons per second presents one ampereof current, the relative sensitivity of the instant device will becomeapparent. As a consequence, the mechanical structuring of the mountingarrangement for the crystal within the probe 12 is of criticalimportance as is the technique for detecting and treating thesesignificantly small charges representing gamma ray interactions.

Looking to FIG. 2, a more detailed representation of the probe device 12is revealed. The angular orientation of the front portion 20 is shownhaving the noted 30° cant with respect to the central axis of the handgripped portion 22. Device 12 is small having an overall length of about19 cm and portion 22 having a length of about 12.7 cm. The overalldiameter of the cylindrical structure 12 is about 1.9 cm. Experience tothe present, utilizing low energy radiolabeling and achieving very highsensitivity on the part of the probe, for many applications has removedthe need for supplementary forward collimation. The hand grip portion 22carries a preamplifier on an elongate circuit board as represented ingeneral at 44. Depending upon the energies of radiation encountered, theprobe 12 housing is formed of an electrically conductive and thusshielding material which functions to attenuate radiation.

Cable 14 supplies power to the preamplifier to the probe, as well asbias and ground to the crystal and functions to transmit thepreamplifier treated output signals. Cable 14 includes silver claddingcomponents 46 and 48 which are mutually insulated and spaced by apolytetrafluoroethylene cover (TEFLON) 50 which is somewhat loose topermit flexure. The innermost leads, formed of TEFLON insulated silver,of the arrangement at respective lines 52 and 54 carry the outputsignals from the preamplifier 44 and a bias signal, for example 30volts, for application to the rear face of the crystal within the device12. Clad 46 carries a 12 volt power supply for the preamplifier circuit,while outer clad 48 carries ground for the system. An outer siliconrubber cover then is provided at 56.

Looking to FIG. 3, an exploded detail of the nose or forward portion 20of probe 12 is provided. This portion 20 retains a radiation responsivecrystal 114, formed preferably of admium telluride, in a light-tight andmechanically secure orientation while maintaining necessary ground andbias conditions upon it. Generally, such crystals as at 114 will have arigidity or physical consistency somewhat similar to chalk and areformed having very light gold coatings on their surfaces. Thus, themounting of such delicate crystals and their operation within a probeinstrument as at 12 requires a highly refined design architecture.However, it is also important that the structure of the probe 12 be suchas to permit its fabrication in a reasonably practical manner.

FIG. 3 shows the hand-graspable portion as at 22 extending to asupporting tubular portion 70. The forwardly disposed tubular region ofportion 70 including its cylinder connector surface 72 are configuredhaving an internal diameter defining a chamber 74. Chamber 74 receives agenerally cylindrically shaped slug or crystal mount 76 along with aconductive epoxy retainer layer 146 (see FIG. 4) which retains the slug76 in position.

Slug or crystal mount 76 is formed of a suitable radiation attenuatingmaterial such as lead and is of a general cylindrical configuration. Inthis regard, the rearwardly disposed cylindrical surface thereof 78 isconfigured for the notes slideable mounting within chamber 74 of thehousing rearward portion 22. Extending centrally through slug 76 is anaccess opening 80 passing therethrough to a forwardly-disposedcylindrical recess represented generally at 82. Opening 80 functions tocarry an insulated lead 84. Lead 84 functions as a bias-signaltransmission wire leading to the physically adjacent preamplificationstage circuit board 44 within the hand-graspable portion of theinstrument at 22 (See FIG. 2). The cylindrical surface 78 of slug 76 isseen to terminate at a cylindrical collar region thereof 86 which isconfigured having an annular retainer groove 88 formed therein and whichfurther incorporates a bore 90 extending in gas flow communication withthe centrally disposed opening 80. Bore 90 serves to equalize gaspressure between the handle or hand graspable portion 22 of theinstrument and the forwardly disposed components. The bore furtherfunctions to receive a tool for facilitating removal of the slug orcrystal mount 76 and its associated assemblage of components formaintenance purposes and the like.

Within recess 82 there is formed, in situ an electrically insulativelayer 92 which additionally functions as a cushioning mount for thecadmium telluride crystal 114 of the assemblage. Formed from a siliconrubber, the layer 92 is structured such that its external surfacedefines the walls of a crystal receiving cavity represented generally at104, the side surfaces of which are depicted at 94 and the bottomsurface of which is shown at 96. Additionally formed with this materialis an annular depression 98 which is configured to receive acorrespondingly configured bias contact member 100 formed at theterminus of insulated lead 84. Contact 100, for example, may be formedof an electrically conductive copper foil adhesively retained upon theleads within insulated lead 84. With the provision of the depression 98,the bias contact member 100 may be flush mounted along the bottomsurface of the insulative layer which as noted may also serve to providea cushioning effect. The sides 94 of the layer 92 defined cavity 104 areof a length for fully receiving the corresponding sides 97 of thecrystal 114 to be mounted therein. Note that the radiation attenuatingmaterial of the crystal mount 76 at sides 102 forming recess 82 iscoextensive with the side 94 of the cavity 104. This portion of theretainer 76 collar or shoulder 86 functions to block radiation otherwiseincident on the sides of the crystal when it is positioned within theassemblage.

The widthwise extent of the cavity 104 across the inwardly disposedsurfaces of sides 94 thereof is slightly greater than the correspondingwidthwise extent of crystal 114. A spacing or gap 95 (FIG. 4) thus isformed between cavity sides 94 and the side surface 98 of crystal 114.For example, for a cylindrically shaped crystal as depicted, the cavity104 is cylindrically shaped having a slightly greater outer diameterthan the crystal. This small gap 95, for example 0.005 inch, serves toprevent noise phenomena resulting from any contact occurring between theside 97 of the crystal and the cavity 104 sides 94. Accordingly, gap 95is formed having a width effective to avoid electrical noise phenomenawhich otherwise may be generated or occur as a consequence of contactbetween crystal side 97 and cavity side surface 94.

Cavity 104 including side surfaces 94, bottom 96, and depression 98,preferably is formed with a tooling arrangement wherein its shape anddimensions are customized to the corresponding shape and dimension ofthe crystal assemblage to be inserted therein, taking into account theformation of gap 95. Looking to FIG. 5, a tooling arrangement for socustomizing the cavity 104 by the process of molding layer 92 isrevealed. The material used for layer 92 may, for example, be a siliconrubber identified as "Two-Part RTV" rubber marketed by Chembar, Inc.,Groveport, OH 43125. This material is prepared by combining an HF RTVsilastic material with a catalyst in accordance with a predeterminedratio. The material is poured within recess 82 of the crystal retainer76 and a tool 106 which is comprised of a rectangular aligning bar 108,a male crystal mold 110, and a centrally-disposed aligning bar or rod111 is inserted into the deposition. Note that rod 111 protrudesdownwardly into opening 80 and that the mold 110 incorporates acylindrical protrusion 113 functioning to form the earlier-describeddepression 98. In general, the silastic material is located about recess82, whereupon the tool 106 is inserted for an interval sufficient topermit curing. The tool 106 then is withdrawn and the resultant silasticlayer 92 is one which receives the crystal and related components to bepositioned within with the spacing deriving gap 95. While providingelectrical insulation, layer 92 also serves to contribute a cushioningfunction.

Returning to FIG. 3, upon positioning the bias contact member 100 ascoupled with lead 84 within the depression 98 of layer surface 96, anannular of disk shaped electrically conductive compliant member 112 ispositioned over the biasing contact 100 in freely-abuttable fashion. Thecompliant member 112 preferably is formed of a non-waven TEFLON cloth(stretched, highly crystalline, unsintered polytetrafluoroethylene)marked under the trade designation "GORETEX" having a thickness, forexample, of about 0.020 in. and being filled with carbon particles toestablish the requisite electrical conductivity. Component 112 not onlyfunctions to provide an intimate contact with biasing component 100,but, importantly, serves to establish a corresponding electrical contactwith the radiation responsive crystal 114. The rearwardly disposed face116 of crystal 114 freely abuts against the conforming surface ofcomponent 112 to develop an intimate and surface-conforming electricalcontact. Additionally, the component 112 serves the important functionof cushioning the delicate crystal 114.

Ground potential is applied to the opposite or forwardly-disposed face118 of crystal 114. This is carried out by positioning anotherconductive and compliant member 120, which may be configured identicallyas member 112, (carbon filled non-woven TEFLON) in freely abuttablefashion over surface 118. As before, the component 120 serves to providea freely-abutting electrical contact through a conforming intimacy withsurface 118. To establish a ground potential, four thin platinum wires122-125 are provided which are swaged within respective grooves 128-131formed within surface 102 of slug 76 as seen in FIG. 6. The wires122-125 then are bent over as shown in FIG. 6 to contact theforwardly-disposed surface of compliant member 120. This sub-assembly issecured by a small disk 134 of transparent tape.

The small, thin platinum wires 122-125 establish an appropriate groundcondition at the forward face 118 of crystal 114 through member 120while imposing only a very minimal potential blockage of any impingingradiation. To enhance and stabilize the electrical contact both fromwires 122-125 and the biasing contact member 100, the assemblage of disk134, compliant disk 120, crystal 114, compliant disk 112, biasingcontact 100, and layer 92 are retained in a compressive, physically ordynamically stable state by a resilient retainer 1356 which ispositioned in tension over the noted assembly and retained in suchtension by a conventional elastic O-ring 138 which engages the retainer136 within groove 88 of crystal retainer or slug 76.

Looking additionally to FIG. 7, the retainer 136 is represented as aresilient web which may be formed of nylon or the like. The web ispositioned over the noted assemblage of components and drawn downwardlyover them as well as over the outer surface 102 of retainer 76 to beretained in such tension by the O-ring 138. A simple cup-shaped jig maybe employed for this purpose. The resultant assemblage has been found toboth effect a stabilization of the electrical contacts for biasing andgrounding purposes, and to retain all components in adjacency withcrystal 114 in a desirably statically stable state to avoid thegeneration of motion induced noise.

Returning to FIG. 3, a forward cover 140 is positioned over theabove-described assemblage as it is installed within housing chamber 74.Because of the extension of the radiation shielding material, such aslead, of retainer 76 about the sides of crystal 114 by virtue of theside portions 102, the forward cover 140 may be made entirely andunitarily of a convenient radiation transmissive material such asaluminum. This avoids the formation of junctions at the periphery ofwindow component 18 which may be prone to break down and consequentlypermit ingress of fluids and the like from the surgical theater. Becausethe cover 140 functions as an electrical shield, the interior sidesurfaces thereof are made electrically conductive by the depositionthereof of a thin layer of gold as at 142. Finally, the external surfaceof the cover 140 preferably is coated with a polymeric low surfacefriction coating 144. This layer 144 may, for example, be provided asTeflon. The coating functions to aid in avoiding friction generatednoise occasioned by the movement of the device over tissue and theimplements typically encountered in a surgical theater.

Looking to FIG. 4, the final assembly of the instrument portion 20 isrevealed in sectional detail. Note, that the retainer or slug 76 isadhesively coupled to supporting tubular portion 70 with a layer ofelectrically conductive epoxy cement 146, while the forward cover 140additionally is retained over portion 72 of the housing by a conductiveepoxy cement layer 148. Note in FIG. 4 that the assemblage of tubularportion 70, crystal 114, and the components associated therewith are sooriented upon final assembly that a dead space 150 is created betweenthe forwardly-disposed surface 118 of crystal 114, as well as theassociated cushioning, retainer, and electrical contact components, andthe window portion 18 of cover 140. This dead air space provides anenhancement of acoustic isolation of the crystal 114.

As represented at circuit 44 in FIG. 2, in order to carry out thetreatment of the very faint charges which are evolved due to gammainteraction with crystal 114, it is important that the preamplificationfunction take place as close as possible to the situs of theinteraction. In view of the operational need in surgery for the 30° cantof the central axis of the forward portion 20 with respect to thecorresponding axis of the rearward support portion 22 of the probe 12,the small length of transmission wire 84 is required. Because extremelysmall charges of current age involved in the range of 300-600atto-coulombs, a preamplification stage which performs to achieve a veryhigh gain is called upon but one which performs with low noisegeneration. In effect, the preamplification stage of the instantapparatus is one achieving a voltage amplification, for example on theorder of about 25,000.

Crystal 114 is maintained in a carefully electrically shielded,acoustically dead and light-tight environment. Aluminum cover 140permits entry of very low level emissions of gamma radiation. Thus, thefull forward face 118 of crystal 114 is exposed to radiation. Eventhough the window 18 portion of the cover 140 is relatively broad inextent, the capability of the instrument 12 to differentiate theinterface between tissue carrying radiolabelled antibodies and the likeand those not carrying these labels is quite accurate to the extent thatcollimation to achieve close differentiation typically is not required.

A technique which both simplifies cleaning the instrument andmaintaining its sterile condition involves the use of a disposableplastic cover which fits over the probe device 12 and which is formed ofa polymeric material which is readily produced in a sterile state. Thus,prior to an operation, the surgical personnel will slide the probewithin the cover or sheath. The addition of the polymeric surface aidsin the control of vibration induced noise as well as representing anideal technique for maintaining the requisite sterile condition for thedevice. Looking to FIG. 8, the instrument 12 is shown in dashed linefashion with a polymeric cover 154. Cover 154 includes a nose portion156 formed of a tough plastic having a thickness, for example, of 0.020inch. This will protect the cover 154 from tearing or the like when usedin the rigorous activities of surgery. From the nose portion 156 thesheath may extend rearwardly a sufficient length to cover the signaltransmission components as at 14 for a sufficient distance to assuresterile integrity.

Referring to FIGS. 9A and 9B, a block diagrammatic representation of theinstrumentation circuitry is revealed. In FIG. 9A, the cadmium telluridecrystal 114 is shown having one face coupled to ground through line 157,while the opposite, biased face thereof is coupled via lines 158 and 159to a bias filter represented at block 160. The input to the filter 160is represented at line 161 as being applied through the triaxial cableas described earlier at 14 and represented by that numeral herein. Line158 corresponds with the earlier-described line 62 in FIG. 2. This biasemanates from a power supply shown at block 162 in FIG. 9B andrepresented at line 163.

Line 158 from the crystal 114 is shown extending to an integrator stage164 of the preamplifier 44. The integrated valuation of detectedradiation disturbance then is shown directed as represented by line 165to a drive-amplification network shown at block 166. A 12 v power supplyis provided from the power supply 162 (FIG. 9B) as represented at line167 which, as shown in FIG. 9A, is directed to a probe current networkrepresented by block 168. Under microcomputer control as represented byline 169, the network 168 develops signals, for example, determiningwhether the probe instrument 12 has been properly connected to theconsole 16. Delivery of the 12 v power supply for the preamplifier stage44 is represented at line 170 as extending to the drive amplifier fromcable 14 via line 171. Line 171 corresponds with the clad 46 describedin conjunction with cable 14 in FIG. 2.

Ground to the instrument 12 also is developed from the power supplyblock 162 as represented at line 172 shown in FIG. 9A as extending tocable 14 and via line 173 to the instrument preamplification components44. Line 173 corresponds with the earlier-described clad at 48 in FIG.2.

The output of the preamplification circuit 44 is represented at line 174extending through the cable representation 14 corresponding with theearlier-described line 54 in FIG. 2. Line 174 extend from the cable 14as line 175 to the input of a normalizing amplifier represented at block176. The network represented by block 176 functions to amplify orattenuate, ie. scale the noise characteristic of any given instrument 12and normalize the value thereof or render it consistent for layercomparison stages. Generally, for example the 27 kev energy level gammaray generated pulses in the system will be about five times higher thannoise levels. Normalizing amplifier network 176 will establish thosenoise levels at some predetermined level, for example, 200 millivoltsand the resultant proportional valid gamma related pulses will becomeabout one volt high for purposes of ensuing comparison functions. It maybe observed that the amplifier network at block 176 is shown controlledfrom a digital-to-analog converter network represented at block 177 vialine 178. Network 177, in turn, is controlled from line 179 extending,as shown in FIG. 9B, to block 180 representing a microcomputer network.The normalized output developed from network 176 is presented alonglines 181 and 182 to a noise average circuit as represented at block183. This network 183 determines in average amplitude value for thenoise of a given system with a given instrument 12 and provides acorresponding signal as represented at line 184 (noise amp) which isemployed as above-described as information used by the microcomputer180. This information, in addition to being employed with thenormalizing amplifier network represented at block 176 may be used todevelop a low window valuation for the comparison function.

Line 182 also extends via line 186 to a pulse acquire networkrepresented at block 188. This network functions, when activated by themicrocomputer represented at block 180, to acquire the value of thehighest pulse amplitude witnessed at line 186. Periodically, thisinformation then is transmitted to the microcomputer at block 180 asrepresented by line 190. Representing a form of peak detector, thenetwork is sometimes referred to as a "snapshot circuit". Also producedfrom line 182, as at line 192 and block 194 is a buffer amplifier whichwill provide at line 196 an output representing received pulses whichmay be made available at the rearward portion of console 16 forconventional radiation evaluation purposes.

Line 181 extends, as shown in FIG. 9B at line 198, to one input of anupper window comparator represented at block 200 and a lower windowcomparator illustrated at block 202. The threshold level for comparativepurposes employed by the network at block 202 is shown asserted fromline 204 and, preferably, is developed by the logic of microcomputernetwork 180 at a level just above the noise amplitude signals generatedfrom line 184. Of course, manual setting of such windows can be carried,out. In similar fashion, the upper window of acceptance for valid gammaray interaction is established from a corresponding line 206. Thisthreshold setting may be made from the information taken from pulseacquire network 188.

Returning to FIG. 9A, the upper window and lower window thresholdselections are made under the control of the microcomputer network atblock 180 as controlled from the digital-to-analog network shown atblock 177. It is the characteristic of such networks as at block 177 toprovide an output which is comprised, for example, of 256 steps ofvarying amplitude. The percentage of incrementation from step-to-stepwill vary somewhat over the range of voltage values provided.Accordingly, the outputs from this conversion network at block 177, asat lines 208 and 210 are directed to squarer networks shown,respectively, at blocks 212 and 214. These networks function to squarethe current outputs at lines 208 and 210 and thus achieve a uniformpercentage incrementation of the threshold defining outputs at lines 204and 206.

Returning to FIG. 9B, the outputs of the comparator networks shown atblocks 200 and 202 represent candidate pulses which may be above orbelow the given thresholds and are identified as being presented as a"UW pulse" and an "LW pulse" along respective lines 216 and 218. Theselines are shown directed to a real time pulse discriminator networkrepresented at block 220 which carries out Boolean logic to determinethe presence or absence of valid pulses. Valid pulses are introduced tothe microcomputer network 180 as represented by line 222.

The microcomputer represented at block 180 performs under a number ofoperational modes to provide both audio and visual outputs to aid thesurgeon in locating and differentiating tumorous tissue. In the formerregard, as represented at line 224 and block 226, a volume controlfunction may be asserted with amplitude variations controlled from asolid-state form of potentiometer as represented at line 228 and block230. Further, a "siren" type of frequency variation may be asserted asrepresented at line 232 to an audio amplification circuit represented atblock 234 for driving a speaker as represented at 236 and line 238. Withthe noted siren arrangement, the frequency output from speaker 236increases as the instrument 12 is moved closer to the situs ofconcentrated radiation. Of course, conventional clicks and beeps can beprovided at the option of the operator.

The microcomputer network 180, as represented by arrow 240 and block 242also addresses an input-output network which, as represented at arrow244, functions to provide a pulse count output of varying types as wellas outputs represented volume levels, pulse height, noise levels andbattery status. Visual readout is represented in FIG. 9B as a block withthe same display 26 numeration as described in conjunction with FIG. 1.Similarly, the input-output function represented at block 242 providesappropriate scanning of the keyboard or switches described inconjunction with FIG. 1 at 30 and represented by the same numeration inFIG. 9B. During the counting operation, the microcomputer network 180functions to control a light emitting diode drive network represented byblock 246 from line 248. The drive network represented at block 246 isshown providing an input, as represented by line 250 to the dual LEDdisplay as described at 28 in FIG. 1 and represented in block form withthe same numeration. This readout provides a red light when a gamma rayis detected and a green light during the counting procedure in general.A serial output port of conventional variety also is provided on theconsole 16, such ports being represented at block 252 being addressedfrom the microcomputer at block 180 from line 254 and having output andinput components represented by arrow 256. A real time clock-calendarhaving a non-volatile memory also may be provided in conjunction withthe functions of the microcomputer network 180 as represented by block258 and arrow 260. Further, the microcomputer may be employed to monitorthe performance of the power supply represented at block 162. This isshown being carried out by the interaction of the microcomputer networkwith a multiplexer represented at block 262 and having an associationrepresented by arrows 264 and 266. It may be observed that the powersupply also provides a +5 v source for the logic level components of thecircuit as represented by line 268; a -5v source at line 270, as well asa -9v reference at line 272 for display 26 drive and, finally, a 2.5vreference as represented at line 274 to provide reference input tot heanalog circuitry described later herein.

Returning to FIG. 9A, the microcomputer network as represented at block180 also provides an input to the digital-to-analog conversion networkrepresented at block 177 which corresponds with the instantaneous pulserate and this information is conveyed to a pulse rate amplifier networkrepresented at block 276 via line 278. The resultant output asrepresented at line 280 may be provided, for example, at the rear of theconsole 16. This circuit represented at block 276 also may be employedto generate a calibrating pulse for testing the downstream components ofthe system. Thus, the microcomputer applies a predetermined pulse levelthrough the digital-to-analog conversion network at block 177 forpresentation to the amplifier network represented at block 276. Theresultant output at line 282 is selectively switched as represented byblock 284 to define pulse width from the microcomputer input at line 286to the calibrating pulse at line 288.

Since certain changes may be made in the above-described system andapparatus and method without departing from the scope of the inventionherein involved, it is intended that all matter contained in thedescription thereof or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

I claim:
 1. An instrument for detecting and locating sources ofradiation emission having predetermined energy levels, comprising:ahousing having a forwardly disposed portion; a crystal mount positionedwithin said housing forwardly disposed portion, formed of materialattenuating radiation of said predetermined energy levels and having aforwardly disposed crystal receiving cavity having sidewalls extendinginwardly thereinto from a forwardly disposed opening; a resilient,electrically insulate polymeric layer within said cavity having anoutwardly disposed electrically insulative surface; a radiationresponsive crystal located within said cavity having a rearwardlydisposed surface positioned facing said electrically insulative surfaceand having a side portion extending to a forwardly disposed surface;biasing means extending within said cavity and having a bias contactadjacent said electrically insulative surface; a first electricallyconductive compliant member conformable with and in contacting adjacencybetween said crystal rearwardly surface and said bias contact; a secondelectrically conductive compliant member conformable with and incontacting adjacency with said crystal forwardly disposed surface;grounding means positioned in abutting adjacency with said secondcompliant member for electrically grounding said crystal forwardlydisposed surface; resilient retainer means positioned in tension oversaid grounding means, said second electrically conductive compliantmember and said crystal forwardly disposed surface for compressivelyretaining components including said grounding means and said secondcompliant member against said crystal forwardly disposed surface andsaid rearwardly disposed surface against said first compliant member,and bias contact, and said resilient polymeric layer to an extenteffective to provide a stabilization of the electrical contacts to saidcrystal derived from said basing means and said grounding means and toretain said components in a statically stable state; and forward covermeans positioned over and enclosing said crystal mount crystal receivingcavity, said crystal, said grounding means, and said resilient retainermeans for permitting transmission of said radiation emission of saidpredetermined energy levels.
 2. The instrument of claim 1 in which saidelectrical bias contact is in freely-abutting contact with said firstelectrically conductive compliant member.
 3. The instrument of claim 1in which said first electrically conductive compliant member is acarbon-filled non-woven polytetrafluoroethylene cloth.
 4. The instrumentof claim 1 in which said grounding means comprises an electricallyconductive member extending over and in freely-abutting contact withsaid second electrically conductive compliant member.
 5. The instrumentof claim 1 in which said second electrically conductive compliant memberis a carbon-filled, non-woven polytetrafluoroethylene cloth.
 6. Theinstrument of claim 1 including a polymeric, low surface frictioncoating located over the outwardly disposed surface of said forwardcover means.
 7. The instrument of claim 1 including a disposable,sterile, thin polymeric cover positionable over said instrument forisolating the components thereof from contaminants and presenting asterile instrument exterior for surgical utilization.
 8. The instrumentof claim 1 in which:said grounding means comprises a wire leadelectrically coupled with said housing and extending over and infreely-abutting contact with said second electrically conductivecompliant member.
 9. The instrument of claim 1 in which said groundingmeans comprises a wire lead fixed to and supported from said crystalmount and extending over and in freely-abutting contact with said secondelectrically conductive compliant member.
 10. The instrument of claim 1in which said resilient retainer means is a resilient web positioned intension over said second electrically conductive compliant member andfixed in tension to said crystal mount.
 11. The instrument of claim 1 inwhich said crystal mount crystal receiving cavity is configured having adepth at least coextensive with said crystal side portion so as toattenuate radiation otherwise incident thereon.
 12. The instrument ofclaim 1 in which:said bias contact is in freely-abutting contact withsaid first electrically conductive compliant member; said groundingmeans comprises an electrically conductive member extending over and infreely-abutting contact with said second electrically conductivecompliant member; and said resilient retainer means is a resilient webpositioned in tension over said grounding means and fixed to saidcrystal mount so as to effect a compressive retention of said groundingmeans against said second compliant member and said second compliantmember against said crystal forwardly disposed surface.
 13. Theinstrument of claim 12 in which said first and second electricallycompliant members are carbon-filled, non-woven polytetrafluoroethylenecloth.
 14. The instrument of claim 13 in which said resilient retainermeans is a nylon web.
 15. An instrument for detecting sources ofradiation emissions, comprising:a housing having a forwardly disposedportion; a crystal mount positioned within said housing forwardlydisposed portion having an electrically insulative forwardly disposedcrystal supporting surface; a radiation responsive crystal having arearwardly disposed surface positioned facing said crystal mount crystalsupporting surface and having a side portion extending to a forwardlydisposed surface; electrical biasing means having a bias contact at saidcrystal mount crystal supporting surface; a first electricallyconductive compliant cushioning member conformable with and incontacting adjacency between said crystal rearwardly disposed surfaceand said bias contact; a second electrically conductive compliantcushioning member conformable with and in contacting adjacency with saidcrystal forwardly disposed surface; grounding means positioned inadjacency with said second compliant member for electrically groundingsaid crystal forwardly disposed surface by electrical associationtherewith through said second compliant member; a resilient web retainerpositioned in tension over said grounding means and said secondelectrically conductive compliant cushioning member for compressiblyretaining components including said grounding means, said secondelectrically conductive compliant cushioning member, and said crystaland said first electrically conductive compliant cushioning member uponsaid crystal mount supporting surface to an extent effective to providea stabilization of the electrical contacts to said crystal derived fromsaid biasing means and said grounding means and to retain saidcomponents in a statically stable state; and a forward cover positionedover and in enclosing relationship with said crystal mount crystalsupporting surface, said crystal, said grounding means, and said firstand second electrically conductive compliant cushioning members forexcluding external contaminants, and having a forwardly disposed windowportion formed of material permitting substantial transmission of saidradiation emissions to said crystal forwardly disposed surface, saidwindow portion being spaced forwardly from said crystal to define a deadair space for enhancing the acoustic isolation of said crystal.
 16. Theinstrument of claim 15 in which said crystal mount crystal supportingsurface is within a crystal receiving cavity having sidewalls spacedfrom said crystal side portion to define a gap therebetween of dimensioneffective to avoid the generation of electrical noise phenomena, saidcrystal receiving cavity being configured a depth at least coextensivewith said crystal side portion so as to attenuate radiation otherwiseincident thereon.
 17. The instrument of claim 15 in which saidelectrical biasing means is in freely abutting contact with said firstelectrically conductive compliant cushioning member.
 18. The instrumentof claim 15 in which said grounding means comprises an electricallyconductive wire member extending over and in freely abutting contactwith said second electrically conductive compliant cushioning member.19. The instrument of claim 15 in which said first electricallyconductive compliant cushioning member is a carbon-filled non-wovenpolytetrafluoroethylene cloth.
 20. The instrument of claim 15 in whichsaid second electrically conductive compliant cushioning member is acarbon-filled non-woven polytetrafluoroethylene cloth.
 21. Theinstrument of claim 15 including a disposable, sterile, thin polymericcover positionable over said instrument for isolating the componentsthereof from contaminants and presenting a sterile instrument exteriorfor surgical utilization.
 22. The instrument of claim 15 in which saidresilient retainer web is fixed in tension to said crystal mount. 23.The instrument of claim 15 in which said resilient retainer is a nylonweb.
 24. An instrument for detecting sources of gamma radiationemissions, comprising:a housing having a forwardly disposed portion; acrystal mount positioned within said housing forwardly disposed portionhaving an electrically insulative, forwardly disposed crystal supportingsurface; a gamma radiation responsive crystal having a rearwardlydisposed surface positioned facing said crystal mount crystal supportingsurface and having a side surface extending to a forwardly disposedsurface; compliant cushioning means for locating said cyrstal upon saidcrystal supporting surface with substantial immunity from externallyinduced vibration phenomena; electrical biasing means for applying anelectrical bias to said crystal rearwardly disposed surface; groundingmeans for electrically grounding said crystal forwardly disposedsurface; a resilient web retainer positioned in tension over andcompressively retaining components including said gamma radiationresponsive crystal, said compliant cushioning means, said electricalbiasing means and said grounding means for effecting the retentionthereof in compression upon said crystal mount crystal supportingsurface to an extent effective to provide a stabilization of electricalcontacts to the crystal derived from said biasing means and saidgrounding means and to retain said components in a statically stablestate; and a foward cover positioned over and in enclosing relationshipwith said crystal mount crystal supporting surface, said crystal, saidcompliant cushioning means, and said grounding means for excludingexternal contaminants, and having a forwardly disposed window portionformed of material permitting substantial transmission of said gammaradiation to said crystal forwardly disposed surface, said windowportion being spaced forwardly from said crystal to define a spaceenhancing the isolation of said crystal from externally inducedvibration phenomena.
 25. The instrument of claim 24 in which:saidcompliant cushioning means is electrically conductive; and saidgrounding means is configured to assert ground to said crystal forwardlydisposed surface through said compliant cushioning means.
 26. Theinstrument of claim 24 in which:said compliant cushioning means iselectrically conductive; and said electrical biasing means is configuredto apply said electrical bias to said crystal rearwardly disposedsurface through said compliant cushioning means.
 27. The instrument ofclaim 24 including a disposable, sterile, thin polymeric coverpositionable over said instrument for isolating the components thereoffrom contaminants and presenting a sterile instrument exterior forsurgical utilization.
 28. The instrument of claim 24 in which saidresilient retainer means is a nylon web.
 29. The instrument of claim 24in which said compliant cushioning means is a carbon-filled, non-wovenpolytetrafluoroethylene cloth.
 30. An instrument for detecting andlocating sources of radiation emission having predetermined energylevels, comprising:a housing having a forwardly disposed portion; acrystal mount positioned within said housing forwardly disposed portion,formed of material attenuating radiation of said predetermined energylevels and having a forwardly disposed crystal receiving cavity having asidewall extending inwardly thereinto to an electrically insulativesurface from a forwardly disposed opening. a radiation responsivecrystal located within said cavity having a rearwardly disposed surfacepositioned facing said electrically insulative surface and having a sideportion extending to a forwardly disposed surface, said crystal sideportion being spaced from said crystal receiving cavity sidewall adistance selected to effect a substantially non-contacting relationshiptherebetween; biasing means extending within said cavity and having abias contact adjacent said electrically insulative surface; a firstelectrically conductive compliant member conformable with and incontacting adjacency between said crystal rearwardly disposed surfaceand said bias contact; a second electrically conductive compliant memberconformable with and in contacting adjacency with said crystal forwardlydisposed surface; grounding means positioned in abutting adjacency withsaid second compliant member for electrically ground said crystalforwardly disposed surface; resilient retainer means positioned intension over said grounding means, said second electrically conductivecompliant member and said crystal forwardly disposed surface forcompressively retaining said grounding means and said second compliantmember against said crystal forwardly disposed surface and saidrearwardly disposed surface against said first compliant member and saidbias contact; and forward cover means positioned over and enclosing saidcrystal mount, said crystal, said grounding means, and said resilientmeans for permitting transmission of said radiation emission of saidpredetermined energy levels.
 31. The instrument of claim 30 in whichsaid radiation responsive crystal side portion is spaced from saidcrystal receiving cavity sidewall a distance of about 0.005 inch. 32.The instrument of claim 30 including a disposable, sterile, thinpolymeric cover positionable over said instrument for isolating thecomponents thereof from contaminants and presenting a sterile instrumentexterior for surgical utilization.
 33. An instrument for detecting andlocating sources of radiation emission having predetermined energylevels, comprising:a housing having a forwardly disposed portion; acrystal mount positioned within said housing forwardly disposed portion,formed of material attenuating radiation of said predetermined energylevels and having a forwardly disposed crystal receiving cavity having asidewall extending thereinto to an electrically insulative surface froma forwardly disposed opening; a radiation responsive crystal locatedwithin said cavity having a rearwardly disposed surface positionedfacing said electrically insulative surface and having a side portionextending to a forwardly disposed surface, said crystal side portionbeing spaced from said crystal receiving cavity sidewall to define a gaptherebetween effective to avoid the generation of electrical noisephenomena; biasing means extending within said cavity and having a biascontact adjacent said electrically insulative surface; a firstelectrically conductive compliant member conformable with and incontacting adjacency between said crystal rearwardly disposed surfaceand said bias contact; a second electrically conductive compliant memberconformable with and in contacting adjacency with said crystal forwardlydisposed surface; grounding means positioned in abutting adjacency withsaid second compliant member for electrically grounding said crystalforwardly disposed surface; resilient retainer means positioned intension over said grounding means, said second electrically conductivecompliant member and said crystal forwardly disposed surface forcompressively retaining said grounding means and said second compliantmember against said crystal forwardly disposed surface and saidrearwardly disposed surface against said first compliant member and saidbias contact; and forward cover means positioned over and enclosing saidcrystal mount, said crystal, said grounding means, and said resilientretainer means for permitting transmission of said radiation emissionsof said predetermined energy levels.
 34. An instrument for detectingsources of radiation emissions, comprising:a housing having a forwardlydisposed portion; a crystal mount positioned within said housingforwardly disposed portion having a crystal receiving cavity with asidewall extending inwardly thereinto to an electrically insulativeforwardly disposed crystal supporting surface; a radiation responsivecrystal having a rearwardly disposed surface positioned facing saidcrystal mount crystal supporting surface and having a side portionextending to a forwardly disposed surface, said crystal side portionbeing spaced from said crystal receiving cavity sidewall to define a gaptherebetween of dimension effective to avoid generation of noisephenomena; electrical biasing means having a bias contact at saidcrystal mount crystal supporting surface; a first electricallyconductive compliant cushioning member conformable with and incontacting adjacency between said crystal rearwardly disposed surfaceand said bias contact; and a second electrically conductive compliantcushioning member conformable with and in contacting adjacency betweensaid crystal forwardly disposed surface; grounding means positioned inadjacency with said second compliant member for electrically groundingsaid crystal forwardly disposed surface; resilient retainer meanspositioned in tension over said second electrically conductive compliantcushioning member for compressibly retaining said second electricallyconductive compliant cushioning member, said crystal and said firstelectrically conductive compliant cushioning member upon said crystalmount supporting surface; and a forward cover positioned over and inenclosing relationship with said crystal mount crystal supportingsurface, said crystal, and said first and second electrically compliantcushioning members for excluding external contaminants, and having aforwardly disposed window portion formed of material permittingsubstantial transmission of said radiation emissions to said crystalforwardly disposed surface, said window portion being spaced forwardlyfrom said crystal to define a dead air space for enhancing the acousticisolation of said crystal.
 35. An instrument for detecting sources ofgamma radiation emissions, comprising:a housing having a forwardlydisposed portion; a crystal mount positioned within said housingforwardly disposed portion having a crystal receiving cavity with asidewall extending inwardly thereinto to an electrically insulative,forwardly disposed crystal supporting surface. a gamma radiationresponsive crystal having a rearwardly disposed surface positionedfacing said crystal mount crystal supporting surface and having a sidesurface extending to a forwardly disposed surface, said crystal sidesurfaces being spaced from said crystal receiving cavity sidewall todefine a gap therebetween of dimension effective to avoid the generationof noise phenomena; compliant cushioning means for locating said crystalupon said crystal supporting surface with substantial immunity fromexternally induced vibration phenomena; electrical biasing means forapplying an electrical bias to said crystal rearwardly disposed surface;grounding means for electrically grounding said crystal forwardlydisposed surface; resilient retainer means positioned in tension oversaid gamma radiation responsive crystal, said compliant cushioningmeans, said electrical biasing means and said grounding means foreffecting the retention thereof in compression upon said crystal mountcrystal supporting surface; and a forward cover positioned over and inenclosing relationship with said crystal mount crystal supportingsurface, said crystal, said compliant cushioning means, and saidgrounding means for excluding external contaminants, and having aforwardly disposed window portion formed of material permittingsubstantial transmission of said gamma radiation to said crystalforwardly disposed surface, said window portion being spaced forwardlyfrom said crystal to define a space enhancing the isolation of saidcrystal from externally induced vibration phenomena.
 36. An instrumentfor detecting and locating sources of radiation emission havingpredetermined energy levels, comprising:a housing having a forwardlydisposed portion; a crystal mount positioned within said housingforwardly disposed portion, formed of material attenuating radiation ofsaid predetermined energy levels and having a forwardly disposed crystalreceiving cavity having a sidewall extending inwardly thereinto to anelectrically insulative surface from a forwardly disposed opening. aradiation responsive crystal located within said cavity having arearwardly disposed surface positioned facing said electricallyinsulative surface and having a side portion extending to a forwardlydisposed surface, said crystal side portion being spaced from saidcrystal receiving cavity sidewall a distance of about 0.005 inch;biasing means extending within said cavity and having a bias contactadjacent said electrically insulative surface; a first electricallyconductive compliant member conformable with and in contacting adjacencybetween said crystal rearwardly disposed surface and said bais contact;a second electrically conductive compliant member conformable with andin contacting adjacency with said crystal forwardly disposed surface;grounding means positioned in abutting adjacency with said secondcompliant member for electrically grounding said crystal forwardlydisposed surface; resilient retainer means positioned in tension oversaid grounding means, said second electrically conductive compliantmember and said crystal forwardly disposed surface for compressivelyretaining said grounding means and said second compliant member againstsaid crystal forwardly disposed surface and said rearwardly disposedsurface against said first compliant member and said bais contact; andforward cover means positioned over and enclosing said crystal mount,said crystal, said grounding means, and said resilient retainer meansfor permitting transmission of said radiation emission of saidpredetermined energy levels.
 37. An instrument for detecting andlocating sources of radiation emission having predetermined energylevels comprising:a housing having a forwardly disposed portion; acrystal mount positioned within said housing forwardly disposed portion,formed of material attenuating radiation of said predetermined energylevels and having a forwardly disposed crystal receiving cavity havingsidewalls extending inwardly thereinto from a forwardly disposedopening; a pliant, electrically insulative and cushioning polymericlayer within said cavity having an outwardly disposed electricallyinsulative surface; a radiation responsive crystal located within saidcavity having a rearwardly disposed surface positioned facing saidelectrically insulative surface and having a side portion extending to aforwardly disposed surface; biasing means extending within said cavityand having a bias contact adjacent said electrically insulative surface;a first electrically conductive compliant member conformable with and incontacting adjacency between said crystal rearwardly disposed surfaceand said bais contact; a second electrically conductive compliant memberconformable with and in contacting adjacency with said crystal forwardlydisposed surface; at least one thin grounding wire electrically coupledwith said housing and extending over and in freely-abutting contact withsaid second electrically conductive compliant member. a resilientretainer web positioned in tension over said grounding means, saidsecond electrically conductive compliant member and said crystalforwardly disposed surface for compressively retaining componentsincluding said grounding wire and said second compliant member againstsaid crystal forwardly disposed surface and said rearwardly disposedsurface against said first compliant member, said bais contact, and saidresilient polymeric layer to an extent effective to provide astabilization of the electrical contacts to said crystal derived fromsaid biasing means and said grounding means and to retain saidcomponents in a statically stable state; and forward cover meanspositioned over and enclosing said cyrstal mount crystal receivingcavity, said crystal, said grounding wire and said resilient retainerweb for permitting transmission of said radiation emission of saidpredetermined energy levels.
 38. An instrument for detecting sources ofgamma radiation emissions, comprising:a housing having a forwardlydisposed portion; a crystal mount positioned within said housingforwardly disposed portion having an electrically insulative, forwardlydisposed crystal supporting surface; a gamma radiation responsivecrystal having a rearwardly disposed surface positioned facing saidcrystal mount crystal supporting surface and having a side surfaceextending to a forwardly disposed surface; compliant cushioning meansfor locating said crystal upon said crystal supporting surface withsubstantially immunity from externally induced vibration phenomena;electrical biasing means for applying an electrical bias to said crystalrearwardly disposed surface; a resilient nylon web retainer positionedin tension over and compressively retaining components including saidgamma radiation responsive crystal, said compliant cushioning means,said electrical biasing means and said grounding means for effecting theretention thereof in compression upon said crystal mount crystalsupporting surface to an extent effective to provide a stabilization ofelectrical contacts to the crystal derived from said biasing means andsaid grounding means and to retain said components in a staticallystable state; and a forward cover positioned over and in enclosingrelationship with said crystal mount crystal supporting surface, saidcrystal, said compliant cushioning means, and said grounding means forexcluding external contaminants, and having a forwardly disposed windowportion formed of material permitting substantial transmission of saidgamma radiation to said crystal forwardly disposed surface, said windowportion being spaced forwardly from said crystal to define a spaceenhancing the isolation of said crystal from externally inducedvibration phenomena.
 39. An instrument for detecting sources ofradiation emissions, comprising:a housing having a forwardly disposedportion; a crystal mount positioned within said housing forwardlydisposed portion having an electrically insulative forwardly disposedcrystal supporting surface; a radiation responsive crystal having arearwardly disposed surface positioned facing said crystal mountsupporting surface and having a side portion extending to a forwardlydisposed surface; electrical biasing means having a bias contact at saidcrystal mount supporting surface; a first electrically conductivecompliant cushioning member conformable with and in contacting adjacencybetween said crystal rearwardly disposed surface and said bias contact;a second electrically conductive compliant cushioning member conformablewith and in contacting adjacency with said crystal forwardly disposedsurface; a plurality of thin grounding wires positioned in adjacencywith said second compliant member for electrically grounding saidcrystal forwardly disposed surface by electrical association therewiththrough said second compliant member. a resilient web retainerpositioned in tension over said grounding wires and said secondelectrically conductive compliant cushioning member for compressiblyretaining components including said grounding wires, said secondelectrically conductive compliant cushioning member, and said crystaland said first electrically conductive compliant cushioning member uponsaid crystal mount supporting surface to an extent effective to providea stabilization of the electrical contacts to said crystal derived fromsaid biasing means and said grounding wires and to retain saidcomponents in a statically stable state; and a forward cover positionedover and in enclosing relationship with said crystal mount crystalsupporting surface, said crystal, said grounding wires, and said firstand second electrically conductive compliant cushioning members forexcluding external contaminants, and having a forwardly disposed windowportion formed of material permitting substantial transmission of saidradiation emissions to said crystal forwardly disposed surface, saidwindow portion being spaced forwardly from said crystal to define a deadair space for enhancing the acoustic isolation of said crystal.
 40. Aninstrument for detecting and locating sources of radiation emissionhaving predetermined energy levels, comprising:a housing having aforwardly disposed portion; a crystal mount positioned within saidhousing forwardly disposed portion, formed of material attenuatingradiation of said predetermined energy levels and having a forwardlydisposed crystal receiving cavity having sidewalls extending inwardlythereinto from a forwardly disposed opening; a resilient, electricallyinsulative and cushioning polymeric layer within said cavity having anoutwardly disposed electrically insulative surface; a radiationresponsive crystal located within said cavity having a rearwardlydisposed surface positioned facing said electrically insulative surfaceand having a side portion extending to a forwardly disposed surface;biasing means extending within said cavity and having a bias contactadjacent said electrically insulative surface; a first electricallyconductive compliant member formed of carbon-filled, non-wovenpolytetrafluoroethylene cloth conformable with and in contactingadjacency between said crystal rearwardly disposed surface and said biascontact; a second electrically conductive compliant member formed ofcarbon-filled, non-wove polytetrafluoroethylene cloth conformable withand in contacting adjacency with said crystal forwardly disposedsurface; grounding means positioned in abutting adjacency over saidsecond compliant member for electrically grounding said crystalforwardly disposed surface; resilient retainer means positioned intension over said grounding means, said second electrically conductivecompliant member and said crystal forwardly disposed surface forcompressively retaining components including said grounding means andsaid second compliant member against said crystal forwardly disposedsurface and said rearwardly disposed surface against said firstcompliant member, said bias contact, and said resilient polymeric layerto an extent effective to provide a stabilization of the electricalcontacts to said crystal derived from said biasing means and saidgrounding means and to retain said components in a statically stablestate; and forward cover means positioned over and enclosing saidcrystal mount crystal receiving cavity, said crystal, said groundingmeans, and said resilient retainer means for permitting transmission ofsaid radiation emission of said predetermined energy levels.